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Intel Gallium3D Graphics Driver Performance

02-26-2011, 09:00 AM

Phoronix: Intel Gallium3D Graphics Driver Performance

While Intel remains to be the only major graphics vendor standing strong behind their classic Mesa driver on Linux for open-source support rather than drawing up plans to move to the Gallium3D driver architecture, there is actually available a Gallium3D driver available for Intel hardware. This Intel Gallium3D driver has been around since close to Gallium3D's inception, but it targets the older generations of Intel IGPs and was developed by VMware as a proof of concept. The driver is incomplete, but our testing shows that for those with Intel 945 netbooks and other hardware, the "i915g" driver is usable. In this article are benchmarks showing how this Intel Gallium3D driver compares to Intel's officially supported classic Mesa DRI driver.

I have not really tested how it really performs but I use it on my eee 1000h now.
Could Phoronix specify why i915g is "not nearly as mature as the Radeon or Nouveau Gallium3D drivers"?
I mean, I can run xonotic on it! The only problem is the performance but you don't expect a netbook to have good performance anyway...

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I was actually wondering, and couldn't find an answer for this, whether i915g uses llvmpipe for software fallbacks (like the vertex pipeline, since the GMA950 doesn't do vertex processing in HW). If not, why not? It seems this would provide a pretty good performance benefit for machines with decent CPUs (like my tablet that has a Core 2 Duo and a GMA950).

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Also, since the tested machine runs an Atom processor, it likely wouldn't derive as much benefit from that as my machine. I would be nice to see a test with a machine that has a higher-end processor. I might just have to test this myself.

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I was actually wondering, and couldn't find an answer for this, whether i915g uses llvmpipe for software fallbacks (like the vertex pipeline, since the GMA950 doesn't do vertex processing in HW). If not, why not? It seems this would provide a pretty good performance benefit for machines with decent CPUs (like my tablet that has a Core 2 Duo and a GMA950).

gallium drivers can use llvm for vertex shaders if they are configured to use it. You need to enable llvm in your mesa build to use it.

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Hm. Looks like most of the benchmarks were rather CPU bound anyway (largely the same scores even at different resolutions). But still, the gallium driver's results seem to be 'offset', which either means that it produces more CPU churn (by having more overhead) or it utilizes less of the hardware GPU capabilities, therefore using more software fallback... Probably a combination of both.
Are there some charts of CPU utilization during the benchmarks for both classic and gallium drivers? Or perhaps some data about the amounts of memory I/O?